HPNA, also referred to as HomePNA, is a de facto home networking standard developed by the Home Phoneline Networking Alliance. This technology, building on Ethernets, allows all the components of a home network to interact over the home's existing telephone wiring without disturbing the existing voice or fax services. In the same way a LAN operates, home networking processes, manages, transports and stores information, which enables the disparate devices in a home network such as telephones, fax machines, desktops, laptops, printers, scanners and Web cameras to connect and integrate over a home's unpredictable wiring topology. HPNA technology must coexist with telephone service and comply with FCC Part 68 contained within Subpart 47 of the Code of Federal Regulations.
In conjunction with the transfer of information across a telecommunications network, a networking standard, such as HPNA, often employs modulation techniques to more efficiently transfer the information across the network. For instance, quadrature amplitude modulation (QAM) is one modulation technique that carries information in both an in-phase and quadrature direction and shifts the signal band around a single carrier frequency, enabling thereby a higher rate of information transfer through a given transmission medium.
In QAM, the unit of information transferred is called a “symbol,” which advantageously represents multiple bits of information. Although QAM has no official defined symbol to represent the value (0, 0) (a “zero-amplitude” symbol) when mapped to a Cartesian coordinate system, a de-facto symbol with the value (0, 0) has been generally used to represent such information as an “end of file” condition, an “end of subframe” condition, and so on. For a more detailed presentation of QAM, see “Digital Communications”, 3rd Edition, by John Proakis, pages 178-180 and also see “Wireless Communications” by Theodore Rappaport, pages 270-272, both of which are hereby incorporated by reference in their entirety.
However, in the prior art, interpreting some QAM symbols posed certain troubling issues. For instance, due to such problems as noise on a telephone line or other transmission medium, the received symbol may not fit exactly in a given constellation of symbols. This can lead to an ambiguity of interpretation of the received symbol. The zero-amplitude symbol is no exception.
However, when using QAM, accurately defining the area or zone of the Cartesian plane that should correspond to a received zero-amplitude symbol has been unsatisfactory. Accordingly, what is needed in the art is a system and method that more accurately interprets a potential zero-amplitude symbol that overcomes the deficiencies of the prior art.